Red cell antibodies in pregnancy: there is no 'critical titre'.

The purpose of this study was to determine the predictive value and reliability of using a 'critical titre' when assessing the ability of red cell alloantibodies to cause haemolytic disease of the newborn. Titration studies and clinical follow-up of 418 antenatal cases where the mothers had red cell antibodies were studied retrospectively. The antibody specificities were anti-D (n = 359), anti-c (n = 34), anti-E (n = 19) and anti-K (n = 6). Depending on the titre being lower or higher than 16 in the indirect antiglobulin test, the severity of disease was established on the given therapy. Anti-D antibodies with a titre 16 were present in 20% of all cases associated with transfusion need of the child; for anti-c, -E and -K the figure was 4%. Titres > or = 16 resulted in both groups in 50% of the cases in phototherapy only, or no therapy at all. Titres are therefore not reliable indicators for predicting the severity of haemolytic disease of the newborn. Neither should they be used as a guide to whether or not antenatal intervention is indicated. Alternative quantitative or functional assays that measure cytotoxic lysis or phagocytosis or a combination of both should be performed instead.

No beneficial effect of low-dose fetal intravenous gammaglobulin administration in combination with intravascular transfusions in severe Rh D haemolytic disease.

Recent observations have shown that treatment with high-dose intravenous gammaglobulin (IVIgG) given to the mother may improve fetal outcome in cases of severe Rh D alloimmunization. Unfortunately, the costs of this new method of treatment are too high for routine use. Therefore, we decided to apply this treatment to the fetus and to investigate whether the effect of IVIgG might be attributable to blockade of the fetal mononuclear phagocyte system. We have performed a randomized study in which 20 fetuses with severe Rh D-haemolytic disease (HDN) were treated with intrauterine intravascular red cell transfusions (IUT). In 10 of these 20 cases transfusions were followed by administration to the fetus of low-dose IVIgG (85.7 +/- 11.6 mg/kg by ultrasound-estimated fetal weight because of fetal vascular volume considerations). We compared the number of IUTs, postnatal exchange transfusions, haematocrit (Ht) and haemoglobulin (Hb) values before and after transfusion (s) needed by the newborns of the two groups. No significant differences in the transfusion requirements of the fetuses and in the clinical outcome could be demonstrated. However, the 95% confidence interval for the difference in the improvement of cord blood Ht was too wide for any conclusions. The 95% confidence interval for the difference in the improvement of Hb levels suggests that any clinically relevant advantage of IVIgG on Hb is unlikely.

Protection against Rh D-haemolytic disease of the newborn by a diminished transport of maternal IgG to the fetus.

IgG present in the circulation of newborn infants is predominantly of maternal origin. In cases of severe Rh D alloimmunization, the maternal anti-D anti-bodies may lead to Rh D-haemolytic disease of the newborn. However, an impaired placental transport of maternal IgG could be associated with the protection of the fetus/newborn against haemolytic disease as shown in this case report.

Evidence for the protective effect of maternal FcR-blocking IgG alloantibodies HLA-DR in Rh D-haemolytic disease of the newborn.

In cases of Rh D alloimmunization, strong results in the antibody-dependent cell-mediated cytotoxicity (ADCC) assay (> 80% lysis as compared to that of the standard anti-D serum) are indicative of severe hemolytic disease to occur in the newborn (HDN). However, discrepant cases were found in which the maternal anti-D gave strong ADCC results and the newborns had no or only mild hemolysis. In the majority of these cases the mother had produced monocyte-reactive IgG alloantibodies, mostly with HLA-DR specificity. Such antibodies may be capable of blocking FcR-mediated functions of the fetal MPS, and it has been postulated that they inhibit destruction of anti-D-sensitized red cells. We here describe 2 families in which such discrepancies were noticed. In 1 family, in spite of ADCC results of > 80%, the Rh D-positive second child was born without signs of hemolysis. However, the Rh D-positive third child suffered from very severe hemolytic disease. The mother had produced monocyte-reactive HLA-DR antibodies in the second pregnancy which, however, did not react with the cells of the third child. In the other family, the severely Rh D-alloimmunized mother had lost her fourth child because of intrauterine death due to HDN. The Rh D-positive fifth child was born with only mild HDN and only in this pregnancy had the mother produced such antibodies. These 2 case histories give further evidence that maternal monocyte-reactive alloantibodies, in both these cases directed against HLA-DR antigens, can protect the Rh D-positive child against hemolytic disease in case of severe Rh D alloimmunization.

Protection against immune haemolytic disease of newborn infants by maternal monocyte-reactive IgG alloantibodies (anti-HLA-DR).

The extent to which maternal anti-Rh(D) antibodies support lysis of erythrocytes by monocytes in the antibody-dependent cell-mediated cytotoxicity (ADCC) assay is closely correlated with the severity of Rh(D) haemolytic disease of the newborn infant (HDN). However, in some cases HDN is much milder than would be predicted from the ADCC value. We postulated that maternal ADCC-blocking alloantibodies against paternal antigens on monocytes can protect these infants against severe haemolysis. We studied 13 severely Rh(D)-alloimmunised mothers whose infants showed unexpectedly mild HDN (group I) and 14 women with similar ADCC values but whose infants had severe HDN (group II). 7 group-I women had monocyte-reactive IgG alloantibodies that inhibited lysis by paternal monocytes in the ADCC. No such antibodies were found in group II (p less than 0.01). In 6 of the 7 serum samples with monocyte-reactive antibodies, the antibodies had HLA-DR specificity. Our findings suggest that Rh(D)-positive children of some severely Rh(D)-alloimmunised women may be protected from severe HDN by maternal non-HLA-class-I, IgG alloantibodies against paternal monocyte blood-group antigens. These antibodies may inhibit the mononuclear phagocyte system of the fetus.

Detection of human monocyte-reactive alloantibodies by flow cytometry after selective downmodulation of the Fc receptor I.

Monocyte-reactive human alloantibodies may be of importance in situations such as transfusion reactions and bone marrow and kidney transplantation. So far, only complement-binding monocyte-reactive antibodies can be detected with a cytotoxicity assay. No antiglobulin assays are yet available that also detect noncomplement-fixing monocyte-reactive antibodies. The binding of monomeric IgG with high affinity to the Fc receptor I (FcRI) on monocytes has severely hampered the development of such an assay until now. We report on the selective removal of the FcRI from monocytes to test human sera in a flow cytofluorometry assay for the presence of monocyte-reactive IgG alloantibodies. Selective downmodulation of FcRI was accomplished by incubating the cells with murine monoclonal antibodies against FcRI followed by a second incubation with goat-antimouse IgG polyclonal antibodies. With such modified cells, human complement-binding and noncomplement-binding IgG and IgM alloantibodies against polymorphic determinants of the HLA class I and II glycoproteins, the human monocyte antigen system and polymorphic antigenic determinants of the LFA complex, can be detected in a sensitive and reproducible manner.